You probably don't mean Xray diffraction (crystal structure determination) for identifying the geographical origin.
You probably mean that Xray fluorescence of heavier metallic elements might help. But actually, straight-forward chemical assay ought to pinpoint the origin of an ore, by the elemental analysis.
And why would one use mass spectrometry for this purpose?
to measure isotope ratios that can sometimes be correlated with specific mines.
yup. Spell checked liked it - long week already! lol. X-ray would give almost instant results to known samples. Mass spec would tell if other materials were introduced after mining or during processing(especially left over organic debris of which there is more than you might think). If it is simple ore than not necessary, but if it has been worked then I can get a pretty fast analysis. I know it is not conventional but I have been using it for fast source measure of precious metals for years. Geologists scoff at me; but I have traced several gold veins back to the origin even after the gold has been processed. The local assay office won’t let me in the door! I got the idea from this paper:
I had access to a mass spec and was looking for ways to utilize it to trace metal compounds while working in the semiconductor world. Gold for devices was purported to be five or six nines pure. After some failures of gold coatings I became curious about the source of the gold from suppliers and then found the above paper. I had access to SEM’s also but that is another unconventional use of science story. Mostly I enjoy breaking convention in geo analysis. I am current prospecting an old gold mining district in Northern Nevada to verify if the deposits that are physically close to each other are from the same event. Conventional assay has been inconclusive. So the easy way out was for the geologists to declare them the same. Then this paper came out:
http://pyrite.utah.edu/fieldtrips/SEGFnevada2007/Readings/General_CTD/Cline2005.pdf
Got me thinking.
http://www.themineralgallery.com/goldroom.htm